Enhanced Auto-Monitoring Circuit and Method for an Electrical Device

ABSTRACT

A resettable switching apparatus, useful in a GFCI receptacle, has an auto-monitoring circuit for automatically testing various functions and structures of the device. The auto-monitoring circuit initiates an auto-monitoring routine which, among other things, establishes a test fault situation on either the positive or negative half-wave of the power cycle and determines whether the detection mechanisms within the device appropriately detect the test fault and whether the device would trip in the event of an actual fault. Additional functionality of the auto-monitoring circuit permits automatic verification that the device is properly wired, that is, not miswired, and determines whether the device has reached the end of its useful life.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application contains subject matter related to subject mattercontained in copending U.S. Patent Applications filed on even dateherewith, application numbers not assigned yet, entitled, “SOLENOID COILHAVING AN ENHANCED MAGNETIC FIELD,” by Stephen P. Simonin, “COMPACTLATCHING MECHANISM FOR SWITCHED ELECTRICAL DEVICE,” by Gaetano Bonasiaand Kenny Padro and “REINSTALLABLE CIRCUIT INTERRUPTING DEVICE WITHVIBRATION RESISTANT MISWIRE PROTECTION,” by Gaetano Bonasia et al.,which applications are assigned to the assignee hereof, and the entirecontents of each of which are expressly incorporated herein byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present application relates generally to switched electricaldevices. More particularly, the present application is directed tocircuit interrupting devices, such as ground fault circuit interrupter(GFCI) devices, that switch to a “tripped” or unlatched state from a“reset” or latched state when one or more conditions is detected. Suchdevices consistent with the invention disclosed have a more compactlatching mechanism than conventional devices and provide a reusablefeature that electronically prevents a miswire condition.

2. Description of Related Art

Switched electrical devices having contacts that are biased toward theopen position require a latching mechanism for setting and holding thecontacts in a closed position Likewise, switched electrical deviceshaving contacts that are biased toward the closed position require alatching mechanism for setting and holding the contacts in an openposition. Examples of conventional types of devices include devices ofthe circuit interrupting type, such as circuit breakers, arc faultinterrupters and ground fault circuit interrupters (GFCI), to name afew. Electrical receptacles having built-in ground fault protectioncircuitry, i.e., GFCI receptacles, are ubiquitous. Such protectioncircuitry and the associated mechanisms normally take up a substantialamount of the physical space within a receptacle housing, the size ofwhich is limited by the standard junction boxes in which they must fit.The trend toward including additional safety and other features, manyrequired by evolving industry standards, has made it necessary toeconomize on interior receptacle space wherever possible.

GFCI receptacles typically use a mechanical latch for holding thecontacts closed, and a solenoid, a relay, or some other such actuatingdevice, for tripping the latch to open the contacts when an actual faultis detected or when the mechanism of the device for detecting suchfaults is tested. Typical mechanisms for tripping and resetting thecontacts employ an arrangement in which the axis of the trip solenoidand the motion of a linked latch plate are perpendicular to the axis ofa reset button and/or plunger. Despite the trend toward miniaturization,such arrangements tend to be wasteful of available space.

Additional industry standards for such circuit interrupting devices,either presently accepted or contemplated for the future, include:denying power to the user accessible and/or downstream load terminals ofthe device when AC power is improperly applied to the load sideterminals of the device, known as a miswire condition; testing forproper operation of the device after subjecting the device to a suddenforce, known as the shock, or drop, test; and providing a mechanism bywhich proper operation of the device is periodically confirmed withoutthe need for human intervention, known as self-test. Conventionaldevices that may or may not address one or more of these additionalindustry requirements tend to be too large, ineffective, and/or do notprovide a robust method for confirming proper functioning of the device.

SUMMARY OF THE INVENTION

The invention described herein addresses the issues mentioned aboveregarding conventional circuit interrupting devices. Specifically, theinvention described employs a space-efficient configuration in which themechanical latching arrangement for resetting (closing) the contacts isdisposed inside the trip solenoid, and the reset plunger and thesolenoid are coaxial. A device according to other aspects of theinvention further includes industry compliant means for preventing themiswire condition and automatically testing, among other things, its ownability to detect faults.

A circuit interrupting device according to one aspect of the inventionincludes a pair of conductive line terminals for connecting to an ACpower source, a pair of line conductors each being electrically coupledto a respective one of the conductive line terminals, a test conductorelectrically isolated from the pair of line conductors and a pair ofconductive face terminals configured to receive mating conductors of anelectrical load. A fault detection circuit is further included that hasat least one transformer coil through which each of the pair of lineconductors and the test conductor traverse, the fault detection circuitbeing configured to detect a net current passing through the at leastone transformer and generate a fault detection signal. The circuitinterrupting device also has an interrupting device operable toelectrically couple the pair of line conductors and the pair of faceterminals, an actuator operable to engage the interrupting device toelectrically decouple the pair of line conductors and the pair of faceterminals and an auto-monitoring circuit electrically coupled to thefault detection circuit and the actuator, wherein the auto-monitoringcircuit generates a test net current on the test conductor anddetermines whether the fault detection circuit successfully detects thetest net current passing through the at least one transformer coil.

A circuit interrupting device according to a further aspect of theinvention includes two sets of electrical contacts, each set ofelectrical contacts having a fixed contact and at least one movablecontact biased away from the fixed contact, a latch assembly including acarriage operable to hold one of the movable contacts from each of thesets of electrical contacts, and first and second sets of rigid beams, areset assembly including a user accessible reset button and a plungerhaving a reset flange with an upper surface and a lower surface, theupper surface engaging the first set of rigid beams when the resetbutton is pressed and the lower surface engaging the second set of rigidbeams when the reset button is released and an auto-monitoring circuitelectrically coupled to the latch and reset assemblies, wherein theauto-monitoring circuit is configured to automatically determine whetherthe circuit interrupting device is operating properly.

According to another aspect of the invention an auto-monitoring circuitfor automatically monitoring the performance of a ground fault circuitinterrupting (GFCI) device is provided that includes a microprocessorconfigured to periodically run an auto-monitoring routine based on astored program with a driver coupled to the microprocessor and beingoperable to initiate a test signal representative of a ground fault eachtime the auto-monitoring routine is performed, or run. An end-of-lifeindicator is coupled to the microprocessor which is operable to indicatethat the GFCI device has failed to detect the test signal in apredetermined number of consecutive runs of the auto-monitoring routine.The microprocessor directly drives the end-of-life indicator.

According to yet a further aspect of the invention a method is providedfor operating and testing a ground fault circuit interrupter. The methodincludes periodically running an auto-monitoring routine during which atest current is passed through a sense transformer. The method alsoincludes generating a secondary current at the sense transformer whenthe test current passes through the sense transformer, detecting thesecondary current, generating first and second detection signals whenthe secondary current is detected and measuring the second detectionsignal. To carry out the method according to this aspect additionalsteps of determining if the test current was successfully detected basedon a result of the measuring the second detection signal, generating afail count based on the result of the determining step, the fail countrepresenting a number of times the periodic test current was notdetected, tripping the circuit interrupting device if the fail countreaches a predetermined threshold within a predetermined amount of time,and preventing the circuit interrupting device from being tripped by thefirst detection signal if the fail count reaches a predeterminedthreshold within a predetermined amount of time, are conducted.

According to yet a further aspect of the invention a circuitinterrupting device is provided that includes a hot conductive lineterminal for connecting to the hot conductor of an AC power source and aneutral conductive line terminal for connecting to the neutral conductorof an AC power source. A line conducting means is included for carryingcurrent either from or to each of the hot conductive line terminal andthe neutral conductive line terminal. A detection means is also includedfor detecting a net current passing through a transformer and generatinga detection signal when such a detection occurs. Also, a test conductormeans that is electrically isolated from the line conducting means isincluded for carrying a test net current through the transformer, and anauto-monitoring means is included for generating the test net currentand determining if the detection means is successfully detecting thetest net current.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the disclosed invention are described in detailbelow by way of example, with reference to the accompanying drawings, inwhich:

FIG. 1 is a front perspective view of a GFCI receptacle incorporatingthe resettable switching apparatus of the invention;

FIG. 2 is a rear perspective view of the GFCI receptacle shown in FIG.1;

FIG. 3 is an exploded front perspective view of the receptacle of FIG.1;

FIG. 4 is a front perspective view of the receptacle of FIG. 1, with thefront and rear covers and tamper-resistant mechanisms removed;

FIG. 5 is a rear perspective view of the receptacle depicted in FIG. 4;

FIG. 6 is a rear perspective view of the ground yoke/bridge assembly ofthe receptacle of FIG. 1;

FIG. 7 is a front perspective view of the core assembly of thereceptacle of FIG. 1;

FIG. 8 is a front perspective view similar to FIG. 7 from a differentangle, with bus bars and other components added;

FIG. 9 is a front perspective view similar to FIG. 7 with test and resetbuttons and other components added;

FIG. 10 is a front perspective view similar to FIG. 8 from a differentangle, with some parts removed and others added;

FIG. 11 is a front perspective view in transverse cross-section of thereceptacle in the tripped or unlatched state taken along line 11-11 inFIG. 1;

FIG. 12 is a bottom perspective view of the solenoid used in thereceptacle of FIG. 1;

FIG. 13 is a top perspective view of a contact carriage used in thereceptacle of FIG. 1;

FIG. 14 is a bottom perspective view of the contact carriage of FIG. 13;

FIG. 15 is a side elevational view in transverse cross-section view ofthe contact carriage of FIG. 13 taken along line 15-15;

FIG. 16 is an end elevational view in transverse cross-section of thecontact carriage of FIG. 13 taken along line 16-16;

FIG. 17 is an exploded rear perspective view of the contact carriage ofFIG. 13;

FIG. 18 is a rear perspective view of the reset button assembly used inthe receptacle of FIG. 1;

FIG. 19 is a side elevational view in transverse cross-section of thereset button assembly of FIG. 18 taken along line 19-19;

FIGS. 20, 22, 23, 25 and 26 are front elevational views in transversecross-section similar to FIG. 11 showing an alternate version of thelatching components of the receptacle in progressive states during theresetting process;

FIG. 21 is a front elevational view in cross-section of the state of thelatching components shown in FIG. 20 taken along line 21-21;

FIG. 24 is a front elevational view in cross-section of the state of thelatching components shown in FIG. 23 taken along line 23-23; and

FIG. 27 is a schematic diagram of an exemplary circuit that may beemployed in the receptacle of FIG. 1.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

As described herein, terms such as “front,” “rear,” “side,” “top,”“bottom,” “above,” “below,” “upwardly” and “downwardly” are intended tofacilitate the description of the electrical receptacle of theinvention, and are not intended to limit the structure of the inventionto any particular position or orientation.

Exemplary embodiments of devices consistent with the present inventioninclude one or more of the novel mechanical and/or electrical featuresdescribed in detail below. Such features include a compact latchingmechanism that efficiently utilizes the space within the device housingto provide additional area for additional features and/or components.For example, certain types of GFCI devices accommodate a separate plugon the back side of the device for connecting AC power to the device(e.g., SNAPConnect® devices by Hubbell Incorporated). To accommodate theadditional plug it is beneficial to reconfigure certain componentswithin the device housing, such as the latching mechanism, and make moreefficient use of the given space in the housing. One feature consistentwith this objective is to provide a solenoid for actuating the latchingmechanism that is coaxial with the reset pin.

In addition to providing a space-saving mechanical configuration for thedevices, the present invention further includes novel electricalfeatures as well. For example, one or more of the exemplary embodimentsof the invention include an electrical miswire feature that prevents thedevice from being reset, or latached, until the AC power is properlyconnected to the device, i.e., on the line side of the device as opposedto the face, or load, side. In comparison to mechanical type miswireprevention mechanisms, an electrical solution such as provided with thepresent invention avoids inadvertent failure of the mechanical miswiremechanism due to, for example, dropping the device prior toinstallation. Additional electrical features are also provided inaccordance with exemplary embodiments of the invention, such as,enhanced self-test, or auto-monitoring, features.

Some self-test features and capabilities with respect to GFCI deviceshave been disclosed previously, for example, in U.S. Pat. Nos.6,807,035, 6,807,036, 7,315,437, 7,443,309 and 7,791,848, the entirerespective contents of which are incorporated herein for all that istaught. An auto-monitoring feature consistent with the present inventionis more robust than that which has been previously disclosed. Forexample, additional features are provided related to the determinationof an end-of-life (EOL) condition and actions taken subsequent to suchdetermination. Further exemplary novel electrical and mechanicalfeatures consistent with the invention are described herein below withreference to the figures.

Referring to FIGS. 1 and 2, a GFCI receptacle 10 according to theinvention comprises a front cover 12 having a duplex outlet face 14 withphase 16, neutral 18 and ground 20 openings. The NEMA-standard T-shapedphase openings 16 indicate that this particular exemplary embodiment israted for 20 ampere operation. Face 14 also has a central opening 22 fora reset button 24 flanked by an opening 26 for a test button 28 and anopening 30 for concentric status indicators 32, 34. Rear cover 36 issecured to front cover 12 by four screws 38. Ground yoke/bridge assembly40 having standard mounting ears 42 protrudes from the ends of thereceptacle.

Referring to FIG. 3, the exemplary embodiment shown incorporates twotamper-resistant mechanisms 44 disposed behind face 14, one for eachoutlet of the duplex receptacle. The structure and operation of thesetamper-resistant mechanisms are disclosed in U.S. Pat. No. 7,510,412 toValentin, which issued on Mar. 31, 2009, the entire contents of whichare incorporated herein by reference for all that is taught.

Referring to FIGS. 2 and 5, the exemplary GFCI receptacle 10 shownincludes plug-in arrangement 50 for connection to a source ofelectricity. This arrangement comprises line terminals in the form of aphase blade 52, a neutral blade 54 and a ground blade 56 located in acontoured recess 58 in the back of rear cover 36. The source connectionis made when a mating plug (not shown) wired to an AC power source isplugged into mating recess 58. According to an alternative embodiment,standard wire-insertion and/or screw line terminals may be used insteadof plug-in arrangement 50. Such an alternative embodiment requiresadditional push-in contact holes and/or terminal screws not shown.

Referring to FIG. 6, ground yoke/bridge assembly 40 comprises a mainfull-length member 60 having two rectangular apertures 62 and a roundcentral aperture 64. A ground plate 66 carrying two face groundterminals 68 is riveted, or otherwise securely fixed, to main section60. Ground plate 66 also has a substantially round hole 70 in registrywith aperture 64 of main full-length member 60, through which part of asolenoid coil bobbin and part of a reset button assembly extends whenthe device is fully assembled, as noted in more detail below. Groundblade 56 is riveted or otherwise securely fixed to a bent tab 72 on mainmember 60. An auxiliary grounding plate 74 is also provided.

Referring to FIG. 7, core assembly 80 includes circuit board 82 thatsupports most of the working components of the receptacle, including theGFCI circuit (see FIG. 27), sense transformer 84 and grounded neutraltransformer 85. AC line power is delivered via phase conductor bar 86and neutral conductor bar 88, which respectively carry at their endsphase blade 52 and neutral blade 54. Conductors 86 and 88 are receivedin holes in circuit board 82 and are connected on the underside of board82 (see FIG. 5) to oblique linking conductors 90, 92, respectively. Linecontact arms 94, 96 connect to oblique linking conductors 90, 92,respectively, and pass through transformers 84, 85 with an insulatingseparator 98 therebetween. Line contact arms 94, 96 are cantilevered,their respective distal ends carrying phase and neutral line contacts102, 104, adjacent solenoid 108. The resiliency of the cantileveredcontact arms biases the line contacts 102, 104 toward a lowered (i.e.,open) position where they may rest on a movable contact carriage 106,made of insulating (preferably thermoplastic) material, that surroundsor substantially surrounds solenoid 108.

Referring to FIGS. 8 and 10, phase and neutral face terminals 110, 112are energized through bus bars 114, 116, respectively. Bus bars 114, 116have respective, relatively short, contact arms 118, 120, which carry attheir distal ends contacts 122, 124 aligned with their respectivemovable line contacts 102, 104. As seen, for example, in FIGS. 3 and 4,core assembly 80 is substantially surrounded by an insulating separatormanifold 126, which also serves to compartmentalize i.e., separate, faceterminals 110, 112 and bus bars 114, 116.

The Trip and Reset Mechanism

The components of the trip and reset mechanism will now be described.Referring to FIGS. 11 and 12, solenoid 108 includes a coil bobbin 130having four standoffs 132, which space the solenoid from circuit board82. Conductive pins 134, 136, 138 extend through three of the standoffsand penetrate circuit board 82 where they are soldered to separatecircuit leads (not shown), anchoring the solenoid to the circuit board.Two concentric coils, preferably of the same wire gauge, are wound inseries in the same direction, “W” (see FIG. 12), around bobbin 130comprising an inner coil 140 preferably having about 600 turns, and anouter coil 142 preferably having about 320 turns. Winding of the twoconcentric coils begins at pin 134, to which the inner end of inner coil140 is connected, and proceeds to pin 136, to which the outer end ofinner coil 140 is connected. Winding continues in the same directionwith the inner end of outer coil 142, which is also connected to pin136, and proceeds to pin 138, to which the outer end of outer coil 142is connected. A layer of tape covers outer coil 142.

As explained more fully below, tripping of the GFCI device in the eventof a fault employs an enhanced electromagnetic force combining the forcefrom both coils 140, 142 in series by causing a voltage to be appliedacross pins 134 and 138. Both coils are also energized during reset,when reset switch contact pads 144 on circuit board 82 are electricallyconnected together as described below. Fail-safe tripping of the GFCIdevice in the event of a malfunction, however, involves only inner coil140 by causing a voltage to be applied across pins 134 and 136, creatinga power-denial, end-of-life condition, described further below.

Referring to FIGS. 13-17, contact carriage 106 includes a substantiallytube-like, or cup-like, body 150 having a central recess 152 dimensionedto slidably surround solenoid 108. An end or bottom wall 154 of body 150has four holes 156 positioned and sized to slidably accommodatestandoffs 132 of solenoid 108. External wings 158, 160 of body 150 haverespective recesses 162, 164, which are configured to cradle movableline contacts 102, 104, respectively, alongside and adjacent to solenoid108.

Bottom wall 154 of carriage 106 has on its underside two blind holes 180in which coil springs 182 are seated. Coil springs 182, which abutcircuit board 82 (see FIG. 11), are frictionally retained in holes 180by virtue of the reduced-diameter inner end 181 of each hole (see FIG.15). Bottom wall 154 also has a central hub 184 that projects upwardlyinto recess 152. Central hub 184 has four slots 186 and a centrallocating pin 188 on its underside, as best seen in FIG. 17. Theunderside of bottom wall 154 also has a flat channel 179, and twoanchoring studs 189 for attaching the parts described below. Attachmentof these parts involves heating and flattening anchoring studs 189 tolock all of the parts together, as seen in FIGS. 14 and 16. In theexploded view of FIG. 17, however, which illustrates assembly of theparts, anchoring studs 189 are depicted in their pre-deformed state.

Referring to FIG. 17, leaf spring contact assembly 170, comprising asingle integral member in the embodiment shown, is attached to theunderside of bottom wall 154. Assembly 170 preferably has two pair ofconductive leaf spring contacts 172 cantilevered outwardly from acentral mounting plate 174, which has two mounting holes 176 and acentral locating hole 178. When assembled, mounting plate 174 is seatedin channel 179, with locating pin 188 in locating hole 178 and anchoringstuds 189 in mounting holes 176. In their relaxed state, leaf springcontacts 172 depend from bottom wall 154 at a shallow angle, with theirdistal portions directly above reset contact pads 144 on circuit board82. Except for instances when reset button 24 is pressed, the leafspring contacts 172 remain above circuit board 82, spaced from resetcontact pads 144 (see FIG. 11).

A latch beam assembly 190, comprising a single integral member in theembodiment shown, is also attached to the underside of bottom wall 154.Latch beam assembly 190 includes a pair of opposed latch beams 192 thatproject upwardly from a central mounting plate 194 which abuts mountingplate 174 of leaf spring contact assembly 170. Mounting plate 194 hastwo mounting holes 196 which receive anchoring studs 189, a centrallocating hole 198 which receives locating pin 188, and two laterallocating apertures 199. Latch beams 192 extend upwardly through a pairof opposed slots 186 in central hub 184. Each latch beam 192 istransversely resilient and has an inwardly and downwardly directed latchtab 200 just below a slightly flared tip 202, defining a latchingshoulder 204 that faces generally downward as seen, for example, inFIGS. 15-17.

A pair of opposed, transversely resilient reset beams 206 extend upwardthrough the other pair of opposed slots 186 in central hub 184. Resetbeams 206, in this embodiment, are made of a unitary, one-piece memberhaving a mounting bight portion 208 with opposed locating tabs 210 and acentral locating hole 212. When assembled, the upper surface of bightportion 208 abuts the underside 185 of central hub 184, with locatingpin 188 in locating hole 212. The lower surface of bight portion 208abuts mounting plate 194 of latch beam assembly 190, with locating tabs210 resiliently retained in locating apertures 199. Each reset beam 206has an inwardly and upwardly directed reset tab 214 just below aslightly flared tip 216, defining a reset shoulder 218 that facesgenerally upward as seen in FIGS. 15-17.

The Reset Button Assembly

FIGS. 11, 18 and 19 depict details of the reset button assemblyaccording to one exemplary embodiment of the invention. Reset button 24has four depending side walls 220 surrounding a round central boss 222,which defines, with the side walls 220, an annular seat 224 for a resetspring 226. Each of the two side walls, which are parallel to the sidesof the receptacle, has an outwardly facing retaining tab 228. A resetplunger 230 is fixed to reset button 24 in blind hole 229 within centralboss 222. Reset plunger 230 comprises an elongated upper section 232 ofsubstantially uniform and constant diameter, a wider relatively shortmiddle section 234 having an upper shoulder 236, and a narrower lowersection 238 having a tapered tip 240. Lower section 238 also has anintermediate collar 241 approximately as wide as middle section 234 withan upper shoulder 242 and a lower shoulder 244. A hollow ferrousarmature 250 surrounds and is movable along reset plunger 230. Armature250 has a frustoconical lower end 252 and an upper inner shoulder 254.Armature return spring 48, retained between shoulders 254 and 236, urgesarmature 250 upwardly to abut central boss 222 when at rest. As seen inFIG. 11, retaining tabs 228 of reset button 24 are captured beneathadjacent portions of the face 14 of front cover 12 (when in the trippedor unlatched state) while reset spring 226 rests against ground plate 66to urge reset button 24 and the attached reset plunger 230 upwardly.

The Reset Operation

The reset operation of a device in accordance with the present exemplaryembodiment will now be described with reference to FIGS. 20-26. Some ofthe latching components depicted in these figures are slightly modifiedas compared to those depicted in the earlier figures. Specifically, theembodiment depicted in FIGS. 20-26 has a larger armature 250, and alonger collar 241 on plunger 230. Further, one of the reset beams 206has a downwardly (instead of upwardly) directed tab 215 (see FIGS. 21and 24), which functions similarly aslatch tabs 200 on latch beams 206,thus providing a greater bite on upper shoulder 242 of collar 241 duringlatching.

FIGS. 20 and 21 illustrate the tripped or unlatched state (open contacts102, 122 and 104, 124) just prior to initiating the reset sequence. Inthis state, reset button 24 is in its highest position relative to theface 14 of the housing and protruding with tabs 228 abutting theunderside of front cover 12, which is indicative to a user that thedevice is in the tripped state. Collar 241 nests between the upperportions of latch beams 192 and reset beams 206, with its lower shoulder244 just above the upper edge 218 of reset tab 214 (see FIG. 21).Contact cradle 106 is supported solely by springs 182, which keep leafspring contacts 172 spaced from reset contact pads 144 on circuit board82.

FIG. 22 illustrates the condition of the latch components of FIGS. 20and 21 when reset button is initially being pressed. Specifically, whenreset button 24 is pressed, lower shoulder 244 of collar 241 engages theupper edge 218 of reset tab 214 (see FIG. 21), forcing reset beam 206and the attached contact carriage 106 downward until leaf springcontacts 172 electrically connect reset contact pads 144 on circuitboard 82. This closes a reset circuit which ultimately activates, orenergizes, solenoid 108 to fire on a positive half-cycle of the ACwaveform. Further details of the operation of the reset circuit andother electrical operations of exemplary GFCI devices according to theinvention are provided below in reference to FIGS. 27 and 28.

Referring again to FIGS. 22-26, as the energized solenoid pulls armature250 downward against the bias of spring 256 (see FIGS. 22, 23 and 24),tapered lower end 252 of the armature spreads apart latch beams 192 andreset beams 206, freeing reset tab 214 from lower shoulder 244 of collar241. With pressure still exerted on reset button 24 by the rear, resetplunger 232, including collar 241, move further downward (see FIG. 25)until upper shoulder 242 of collar 241 clears latch tabs 200 on latchbeams 192 and tab 215 on reset beam 206. On the negative, non-firing,half-cycle of the AC waveform, solenoid 108 is instantly de-energized,allowing the compressed armature return spring 256 to retract armature250. It should be noted that although the present embodimentcontemplates the solenoid to be activated on the positive half-cycle ofthe AC waveform when the reset button is pressed and de-activated on thenegative half-cycle, it is also within the scope of the invention thatsolenoid activation occur on the negative half-cycle and de-activationon the positive half-cycle. One having skill in the art would appreciatehow to invert the AC waveform for this purpose, for example, byselectively placing a diode in the reset circuit.

With armature 250 no longer between latch beams 192 and reset beams 206,the beams spring back under their natural bias to their originalpositions, i.e., they spring inward toward each other as shown in FIG.25. Because collar 241 is now below latch tabs 200, lower edges 204 oflatch tabs 200 (see FIG. 16) and the lower edge of tab 215 engage theupper shoulder 242 of collar 241. With no downward force now beingapplied to the contact carriage 106 via reset beam 206, coil springs 182raise the contact carriage to disengage leaf spring contacts 172 fromreset contact pads 144, thus preventing further energizing of thesolenoid. Also, armature 250 rises under the return bias of spring 256.In this “pre-latched” state (see FIG. 25), the movable contacts 102, 104have moved closer to their respective fixed contacts 122, 124, but havenot yet closed with them, i.e., they have not contacted them.

The impact of the top of retracting armature 250 on the underside ofreset button 24 provides a tactile indication to the user that resetbutton 24 can be released. When reset button 24 is released, resetreturn spring 226 pulls the reset button assembly, including collar 241,latch tabs 200 and the now latched contact carriage 106, upward untilcontacts 102, 122 and 104, 124, respectively, are closed (see FIG. 26).In this fully reset state, latch tabs 200, which abut upper shoulder 242on reset plunger 232, hold reset button 24 nearly flush with the face 14of the receptacle, indicating that the device is in the latched, orreset state. This is in comparison to FIG. 20, which shows the highestposition of reset button 24 when in the unlatched, or tripped, state.

According to another embodiment, the above-described reset arrangementcan be incorporated in a GFCI-protected receptacle that also has loadterminals for supplying power to downstream devices. For example, suchan alternative embodiment is readily accomplished by providing anadditional set of phase and neutral contacts at the ends of additionalrespective cantilevered load-side contact arms, which connect to loadterminals, such as terminal screws or push-in contact holes, asdescribed above in regard to line side terminals. In an exemplaryarrangement, one such load contact is positioned below movable linecontact 102 on the phase side of the device, and the other load contactis positioned below movable line contact 104, on the neutral side of thedevice. With the receptacle in the tripped or unlatched state, allcontacts on each side (phase and neutral) are electrically isolated.During the reset operation the movable load contacts rise first, bymovable contact carriage 106, and engage their respective line contacts102, 104, which then rise to engage their respective fixed(face-connected) contacts 122, 124. Alternatively, the positions of themovable load and line contacts could be reversed.

A receptacle according to aspects of the invention also includescomponents for testing the GFCI circuitry and permanently denying powerto the face terminals and to the load terminals, if so equipped, when amalfunction is detected. The arrangement according to one embodimentutilizes a two-stage switch, actuated by pressing the test button, whichis functionally similar to a switch disclosed in U.S. Pat. No. 6,697,238to Bonilla, et al., which issued on Feb. 24, 2004 and which isincorporated herein by reference in its entirety. The first stage of thetest switch closes primary contacts that cause the GFCI supervisorycircuit to simulate a ground fault. If the device malfunctions, forexample, it does not trip/unlatch by energizing the solenoid, continuedpressing of the test button invokes the second stage, which closessecondary contacts in a simple circuit that energizes the solenoid totrip and unlatch the device and blow a fuse to permanently disable thedevice (an end-of-life condition).

Referring to FIGS. 4, 8 and 9, vertically movable test button 28 isdisposed above L-shaped conductive spring arm 260, the lower (vertical)leg 262 of which is anchored in a recess in separator manifold 126. Theupper (horizontal) leg 264 of spring arm 260 is cantilevered with itsfree, distal, end 266 disposed above the top 268 of a rocker contact270. One leg 272 of rocker contact 270 is supported on a lead 274 of aresistor mounted on circuit board 82. The other leg 276 of rockercontact 270 is disposed adjacent one end 280 of a test jumper 282, whichis supported at its other end 284 on another resistor lead 286. A testjumper wire 288 electrically connects spring arm 260 to neutral bus bar116.

When test button 28 is pressed, the distal end 266 of spring arm 260makes contact with the top 268 of rocker contact 270, closing the testcircuit, e.g., to simulate a fault, as described in more detail below.If the device malfunctions, i.e., does not trip/unlatch by energizingthe solenoid, continued pressing of the test button causes leg 276 ofrocker contact 270 to swing out and contact the end 280 of test jumper282. When this occurs, both inner and outer coils 140, 142 of solenoid108 are energized to trip and unlatch the device. Further, under thiscondition, an open circuit is generated, such as by blowing a fuse, topermanently disable the device. According to one aspect of thisexemplary embodiment, an end-of-life indicator, such as a red LED oncircuit board 82, is activated to indicate the end-of-life status. Theglow of the red end-of-life LED is visible on the face 14 through outerlight pipe 34 (see FIGS. 1, 3, 4 and 5).

Tripping the GFCI Device

Tripping, or unlatching, the device and, thus, opening contacts 102, 122and 104, 124, will now be described with reference to FIGS. 20, 23 and26. FIG. 26, for example, illustrates the major components of a GFCIdevice in accordance with embodiments of the invention. Moreparticularly, FIG. 26 illustrates the latching components in the fullyreset state, i.e., with the line and face contacts electricallyconnected. When solenoid 108 is momentarily energized by one or more ofa detected fault, a simulated fault or as a result of another test, orby the fail-safe circuit during testing as a result of an end-of-lifecondition, a magnetic field is generated and solenoid armature 250 isbiased or pulled, e.g., downward in FIG. 23, thus, spreading apart latchbeams 192 and reset beams 206 (see also FIG. 23). This action freeslatch tabs 200 from upper shoulder 242 of reset plunger 232, thus,unlatching carriage 106 and allowing reset spring 226 to raise resetplunger 232 by pushing upward against reset button 24. Carriage 106 isnow free to move and drops due to the natural downward bias of contactarms 94, 96 with movable contacts 102, 104 which rest within recesses162, 164 (see FIG. 13). When movable contacts 102, 104 move downward,they separate from their respective fixed (face) contacts 122, 124. FIG.20 illustrates the mechanism shown in FIG. 23 in the final unlatched,tripped, state with carriage 106, including contacts 172, supportedabove the circuit board and contact pads 144 by coil springs 182. Inthis state, reset button 24 is in its highest position relative to thefront face of the device housing.

The Power-On Status Indicator

A power-on status indicator in the form of a green LED 290 (see FIG. 8)is visible on face 14 through inner light pipe 32 (see FIGS. 1, 3, 4 and5). LED 290 is mounted on a mini-PCB 292, and is electrically connectedto neutral bus bar 116 by its lead 294 and electrically connected tophase bus bar 114 by a jumper 296. Further details of the operation ofthe power-on status indicator are provided below in reference to FIG.27.

FIG. 27 is a schematic of an electrical circuit consistent with one ormore of the exemplary embodiments of the present invention describedabove. More particularly, the circuit shown in FIG. 27 can be employedin a GFCI device as described above with respect to various embodimentsof the invention. The circuit shown in FIG. 27 is consistent with themechanical operation of the invention described above; however, a GFCIdevice consistent with the invention need not employ the preciseelectrical circuit depicted in FIG. 27 and those of ordinary skill inthe art, after viewing FIG. 27 and/or reviewing the description setforth below, would be able to modify certain aspects of the circuit toachieve the same or similar results. Such modifications are contemplatedand believed to be within the scope of the invention set forth herein.

Referring to FIG. 27, an electrical circuit consistent with theoperation of the present invention includes phase line terminal 326 andneutral line terminal 328 for electrical connection to an AC powersource (not shown). Phase conductor 330 and neutral conductor 332 arerespectively connected to the phase and neutral line terminals and eachpass through sense transformer 334 and grounded neutral transformer 336,which are part of a detection circuit described below. By way ofexample, phase and neutral line conductors 330, 332 represent linecontact arms 94, 96, respectively, as described above with respect toone exemplary embodiment of the invention. Line conductors 330, 332 areeach cantilevered with respective fixed ends connected to the lineterminals and each includes a respective movable contact, e.g. contacts102, 104 from the embodiment described above. Face phase and faceneutral conductors 338, 340, respectively, include electrical contacts,for example contacts 122, 124 in the embodiment above, fixed thereto.The face conductors are electrically connected to and, in the embodimentshown are integral with, respective face terminals 342, 344, to whichplug blades would be connected when the electrical receptacle device isin use.

The circuit shown in FIG. 27 also includes optional load phase and loadneutral terminals 346, 348, which electrically connect to a downstreamload, such as one or more additional receptacle devices. Load terminals346, 348, when included, are respectively connected to cantilevered loadconductors 277, 278, each of which includes a movable contact (notshown) at its distal end. The load contacts are disposed betweenrespective phase and neutral line contacts and phase and neutral facecontacts and are coaxial with them such that when one of the pairs ofconductors, i.e., line or load, is moved toward the other, i.e., load orline, and the face conductors, the three sets of contacts will mate andbe electrically connected together, e.g., in the reset state describedabove.

The Detector Circuit

A detector circuit 352 includes transformers 334, 336 as well as a GFCIintegrated circuit device (GFCI IC), 350. GFCI IC 350 can be one of anRV4141 or RV4145 device, both made by Fairchild SemiconductorCorporation, a Fudan FM2141 device, a Crys-Lattice CL4141 device, or itcan be a custom device or circuit. GFCI IC 350 receives electricalsignals from transformers 334, 336 and determines if one or more faults,either real or simulated, has occurred. For example, when a currentimbalance in line conductors 330, 332 occurs, a net current flowsthrough the transformers which causes a magnetic flux to be createdabout the transformers. This flux results in current on the wiresconnecting the transformers to GFCI IC 350 and a signal is, thus,provided to GFCI IC 350, which generates a detection signal on one ormore of its outputs, such as the SCR output.

The current imbalance on line conductors 330, 332 results from either areal ground fault or a test ground fault. A test, or simulated, groundfault is generated by pressing the test switch 354, e.g., test button 28described in the embodiments above regarding the mechanical structureand operation of the invention. As described in further detail below,another condition that causes a flux to be generated at one or more ofthe transformers and, thus, the detection signal to be generated by theGFCI IC, is when the auto-monitoring circuit 370 initiates anauto-monitoring test sequence that includes a current generated onindependent conductor 356.

According to one embodiment, test switch 354 is a two-stage switch whereupon initial activation, or pressing by a user, contacts “a” and “b” areelectrically connected. This results in some of the current flowing inline conductors 330, 332 to be diverted around sense transformer 334 andthrough resistor 358 to the face conductors. By diverting some of thecurrent through resistor 358, an imbalance is caused in the currentflowing in one direction through conductor 330 and the current flowingin the opposite direction through conductor 332. This current imbalance,i.e., net current, is detected by circuit 352 and SCR output of GFCI IC350 is activated.

When the SCR output is activated it turns ON the gate of SCR 360allowing current to flow through fuse 368 and trip coil 362 of solenoid366. The current flowing through trip coil 362 generates a magneticfield that moves an armature within the solenoid, e.g., similar to theaction of armature 250 within solenoid 108 described above. When thesolenoid armature moves, it unlatches a contact carriage, such ascarriage 106 in the embodiment above, and the carriage drops under thenatural bias of the line conductors away from the face conductors andthe optional load conductors, if included. The device is now said to be“tripped,” as a result of the successful manual test sequence, and thedevice is ready to be reset. The time it takes from the moment contacts“a” and “b” of test switch 354 connect until the device is tripped andcurrent no longer flows, particularly through fuse 368 and trip coil362, is so short that fuse 368 remains intact.

If, however, the latching mechanism fails to trip and the line and face(and possibly load) contacts are not separated when test button 354 isinitially pressed, continued pressing of switch 354 results in contacts“a” and “b” becoming disconnected and contacts “a” and “c” beingconnected. When this occurs, current flows from neutral conductor 332through resistor 358 and through both coils of solenoid 366, i.e., failsafe coil 364 and trip coil 362. Further, some of the current continuesto flow through fuse 368 resulting in its destruction and an opencircuit results where fuse 368 was previously. According to thisexemplary embodiment, coils 362 and 364 are concentric and the currentnow flowing through both coils results in a stronger magnetic fieldwithin the solenoid 366. This stronger magnetic field is generated in afinal attempt to trip the device and separate the line contacts from theface contacts, that is, the contacts that failed to disengage normallywhen the test button 354 was initially pressed.

Manual Testing Via the Reset Operation

With continued reference to FIG. 27, as described above with respect tothe mechanical aspects of the invention, closing the reset switch 300,e.g., by pressing reset button 24 as described with respect to the aboveembodiments, also initiates a test operation. Specifically, when resetswitch 300 is closed, a voltage supply output, VS, of GFCI IC 350 iselectrically connected to the gate of SCR 360 through conductor 308,thus, turning the SCR ON and drawing current from line conductor 332through fuse 368, trip coil 362 and SCR 360 and ultimately to ground.The current flowing through coil 362 generates a magnetic field insolenoid 366 and the armature within the solenoid is actuated and moves.Under typical, e.g., non-test, conditions the armature is actuated inthis manner to trip the device, such as when an actual fault or a manualground fault via the test button occurs.

In this particular situation, however, the device is already in thetripped condition, i.e., the line and face (and possibly load) contactsare electrically isolated. In this situation the reset button was mostlikely pressed to re-latch the contact carriage and bring the line andface contacts back into electrical contact. This reset operation isdescribed in detail above in regard to FIGS. 20-26. For example, thecontacts on reset switch 300 in FIG. 27 correspond to contacts 172described above. If the armature of solenoid 366 fails to fire, and thereset mechanism, including the contact carriage described above, failsto engage the reset plunger on its return after the reset button isreleased, the device will not be reset. Accordingly, if, for example,the device is not wired at all, or it is miswired, that is, the deviceis wired with the AC power not connected to the line terminals, e.g.,326, 328, no power is applied to the GFCI IC 350. If no power is appliedto GFCI IC 350 it cannot drive SCR 360 and the device will not be ableto be reset, as described above. Thus, the miswire condition isprevented because the device cannot be reset until AC power is properlyapplied to the line terminals.

The Auto-Monitoring Circuit

With continued reference to the exemplary circuit schematic shown inFIG. 27, a further aspect of the invention not previously mentioned willnow be described with respect to auto-monitoring circuit 370.Auto-monitoring circuit 370 includes a programmable device 301.Programmable device 301 can be any suitable programmable device, such asa microcontroller or a microprocessor, which can be programmed toimplement the auto-monitoring routine as explained in detail below. Forexample, programmable device 301 can be implemented by an ATMEL™microcontroller from the ATtiny 10 family or a Microchip microcontrollersuch as a PIC10F204/206.

According to one exemplary auto-monitoring, or automatic self-testing,routine in accordance with this embodiment, programmable device 301initiates the auto-monitoring routine approximately every three (3)seconds by setting an auto-monitoring test flag. The auto-monitoringtest flag initiates the auto-monitoring routine on the circuitinterrupting device and confirms that the device is operating properlyor, under certain circumstances, determines that the circuitinterrupting device has reached its end-of-life (EOL). Moreover, thisautomatic self-testing routine occurs on either half-cycle of the ACwave, i.e., either the positive or negative half-cycle. When theauto-monitoring routine runs with a positive result, the auto-monitoringcircuit enters a hibernation state until the programmable device setsthe test flag again and initiates another auto-monitoring routine.

If the auto-monitoring routine runs with a negative result, e.g., itcannot be determined that the circuit interrupting device is functioningproperly, a failure counter is incremented and the programmable deviceinitiates another auto-monitoring routine when instructed. In additionto the failure count being incremented, a temporary indication of thefailure can also be provided. For example, a Light Emitting Diode (LED)may be flashed one or more times to indicate the failure to a user. Ifthe failure counter reaches a predetermined value, i.e., theauto-monitoring routine runs with a negative result a predeterminednumber of times, the auto-monitoring routine invokes an end-of-life(EOL) sequence. The EOL sequence then performs one or more of thefollowing functions; (a) indicates that EOL has been reached, forexample, by continuously flashing or illuminating an indicator lightand/or generating an audible sound, (b) attempts to trip the device, (c)prevents an attempt to reset the device, (d) stores the EOL event onnon-volatile memory, e.g., in the event there is a power failure, and(e) clears the EOL condition when the device is powered down.

In accordance with this embodiment, when the programmable devicedetermines it is time to run the auto-monitoring routine, a stimulussignal 302 is turned ON by programmable device 301. When the stimulussignal is turned ON, electrical current flows through resistor 303 andtransistor 304 is turned ON. When transistor 304 is turned ON, currentflows from the 3.3V voltage supply through resistor 305, which is, forexample, a 3k-ohm resistor, and continues through electrical conductor356 and transistor 304 to ground. According to this exemplaryembodiment, electrical conductor 356 is a wire connected at one end toresistor 305, traverses through the centers of sense transformer 334 andgrounded neutral transformer 336 and is looped approximately six (6)times around the cores of these transformers and is connected at itsother end to the collector-emitter of transistor 304. Thus, when thesoftware auto-monitoring test flag is set in device 301 and transistor304 is turned ON, current flows through conductor 356 which comprises anindependent third conductor, e.g., separate from the two, hot/phase andneutral, conductors 330 and 332 that also traverse through the centersof transformers 334 and 336.

If the circuit interrupting device according to the present embodimentis functioning properly, when current flows through third conductor 356,thus creating a net current flow through the transformer, a flux isgenerated at the transformer which is detected by detection circuit 352,including GFCI device 350. In accordance with this embodiment, whendevice 350 detects the flux created at 334, a voltage level is increasedat one of the output ports of device 350, for example at the output portlabeled CAP in

FIG. 27, thus increasing the voltage on line 306. Because conductiveline 306 is connected to a capacitor, 307, the SCR trigger signal 308 ofdevice 350 is delayed for a predetermined period of time, i.e.,determined by the value of capacitor 307. For example, if capacitor 307is a 1.8 nF capacitor and device 350 is an RV4141 device, SCR triggersignal 308 is delayed for 3.333 msec. Further, the CAP output, 306, ofdevice 350 is connected to programmable device 301 via a path thatincludes conductor 309 and diode 310 in series with resistor 311, e.g.,4.7 k-Ohm, which completes a voltage divider with resistor 312, e.g.,1M-Ohm.

According to this embodiment, programmable device 301 has ananalog-to-digital converter (ADC) whose input is connected to conductor309. Accordingly, the ADC of device 301 reads the increasing voltageestablished on capacitor 307. When a predetermined voltage level isreached at the ADC input of programmable device 301, device 301 turnsOFF the auto-monitoring stimulus signal by setting the TST output tologic low, thus, turning off transistor 304 and stopping the currentflow on conductor 356 and, thus, the flux created at transformer 334.When this occurs, it is determined by programmable device 301 that aqualified auto-monitoring event has successfully passed and theauto-monitoring fail counter is decremented if the present count isgreater than zero.

In other words, according to this embodiment an auto-monitoring routineis repeated by programmable device 301 on a predetermined schedule. Forexample, based on the software program installed within the device, theauto-monitoring routine is programmed to be run, as desired, anywherefrom every few seconds to every month, etc. When the routine isinitiated, the flux created at transformer 334 occurs similarly to theway a flux would be created if either an actual ground fault hadoccurred or if a simulated ground fault had been manually generated,e.g., by pressing the test button as described above. That is, wheneither an actual or simulated ground fault occurs, a difference in thecurrent flowing in the phase and neutral conductors, 330 and 332,respectively, is created. This differential, or net, current flowingthrough sense transformer 334 is detected by device 350 which, as aresult, drives SCR 360 to turn ON via conductor 308. When SCR 360 turnsON, current passes through trip coil 362 which trips interrupting device315, i.e., causing the contact carriage to drop, causing the line andface (and possibly load) contacts to separate from each other. Thus,current is prevented from flowing through phase and neutral conductors330 and 332 to the phase and neutral face terminals, 342 and 344,respectively, and the phase and neutral load terminals, 346 and 348,respectively, when external load terminals are included in the device inaccordance with the alternative embodiment discussed above.

In comparison, when the auto-monitoring routine is performed inaccordance with the present invention, no differential current iscreated on the phase and neutral conductors 330, 332 and theinterrupting device 315 is not tripped. Instead, during theauto-monitoring routine, the flux generated at sense transformer 334 isa result of current flowing through a single, independent third,conductor 356, electrically isolated from phase and neutral conductors334, 336. The current generated on conductor 356 is present for only abrief period of time, for example, less than the delay time establishedby capacitor 307, discussed previously.

Thus, if the voltage on conductor 309 and input to the ADC input ofprogrammable device 301 reaches a given voltage within thispredetermined period of time during an auto-monitoring routine, it isdetermined that the detection circuit 352 successfully detected the netcurrent flowing in sense transformer 334 and the auto-monitoring eventhas passed. Accordingly, programmable device 301 determines thatdetection circuit 352, including GFCI device 350, is working properly.Because the net current flowing through sense transformer 334 during theauto-monitoring routine is designed to be substantially similar inmagnitude to the differential current flowing through the transformerduring a simulated ground fault, e.g., 4-6 milliamps, it is determinedthat detection circuit 352 would be able to detect an actual groundfault and provide the proper drive signal to SCR 360 to trip interrupter315.

Alternatively, the auto-monitoring circuit 370 might determine that theauto-monitoring routine has failed. For example, if it takes longer thanthe predetermined period of time for the voltage at the ADC input ofprogrammable device 301 to reach the given voltage during theauto-monitoring routine, it is determined that the auto-monitoring eventfailed. If this occurs, an auto-monitoring fail tally is incremented andthe failure is indicated either visually or audibly. For example,according to one embodiment, the ADC port of programmable device 301 isconverted to an output port when an auto-monitoring event failure occursand a voltage is placed on conductor 309 via the converted I/O port,generating a current to flow on conductor 309, through indicator LED 316and resistor 317 to ground. Subsequently, the ADC I/O port ofprogrammable device 301 is converted back to an input for the nextscheduled auto-monitoring event.

For example, when an auto-monitoring event failure occurs, indicator LED316 illuminates only for the period of time when the I/O port isconverted to an output and an output voltage is generated at that port;otherwise LED 316 remains dark, or non-illuminated. Thus, if theauto-monitoring routine is run, for example, every three (3) seconds,and an event failure occurs only a single time or sporadically, theevent is likely to go unnoticed by the user. If, on the other hand, thefailure occurs regularly, as would be the case if one or more of thecomponents used in the auto-monitoring routine is permanently disabled,the indicator LED 316 would blink at a regular interval, thus drawingattention to the device and informing the user that criticalfunctionality of the device has been compromised. Conditions that causethe auto-monitoring routine to fail include one or more of thefollowing, open circuited differential transformer, closed circuiteddifferential transformer, no power to the GFCI IC, open circuitedsolenoid, SCR trigger output of the GFCI IC continuously high, and SCRoutput of the GFCI IC continuously low.

According to a further aspect of this embodiment, if the auto-monitoringfail tally reaches a predetermined limit, for example, seven (7)failures within one (1) minute, programmable device 301 enters anend-of-life (EOL) state. If this occurs, an audible or visual indicatoris activated to alert the user that the circuit interrupting device hasreached the end of its useful life. For example, when an EOL state isdetermined, the ADC I/O port of programmable device 301 is converted toan output port, similar to when a single failure is recorded asdescribed above, and a signal is either periodically placed on conductor309 via the ADC output port, i.e., to blink LED 316, or a signal iscontinuously placed on conductor 309 to permanently illuminate LED 316.The auto-monitoring routine is also halted at this time.

Additionally, according to a further embodiment, when EOL is determined,programmable device 301 attempts to trip interrupting device 315 in oneor both of the following ways: (a) by maintaining the stimulus signal onthird conductor 356 into the firing half-cycle of the AC wave, and/or,(b) by converting the EOL port of programmable device 301 to an output,if it is currently an input port, and placing a drive signal onconductor 318 to directly drive the gate of SCR 320 to turn SCR 320 ON,thus, enabling it to conduct current and activate the solenoid. Morespecifically, when SCR 320 is turned ON, current is drawn through failsafe coil 364 of dual coil solenoid 366. For example, dual coil solenoid366 includes inner fail safe coil 364, which comprises a 300 turn, 10Ohm, coil, and outer main, trip, coil 362, which comprises an 880 turn,25.5 Ohm, coil.

Accordingly, when it is determined via the auto-monitoring routine thatdetection circuit 352 is not successfully detecting ground faults, e.g.,it does not detect the flux resulting from current flowing in conductor356, or that it is not otherwise generating a drive signal on conductor308 to drive SCR 360 upon such detection, programmable device 301determines EOL and attempts to trip interrupting device 315 by one orboth of two separate methods. Specifically, device 301 attempts todirectly trip interrupting device 315 by either, (a) continuing togenerate the signal on conductor 356, or, (b) directly driving the failsafe coil 364, or, both, (a) and (b). There is one significantdifference, however, between the signal on conductor 356 when theauto-monitoring routine is being run normally, and the signal onconductor 356 that is generated when EOL is determined. That is, underEOL conditions, the signal, e.g., electrical pulse, on conductor 356 isextended into, or otherwise generated in, the firing half-cycle of theAC wave. This should generate flux at transformer 334 which, assumingall else is working properly, causes SCR 360 to be triggered and tripcoil 362 to be energized, thus activating the solenoid to trip theinterrupting device 315.

When the second method (b) above, is employed, that is, SCR 320 isdriven to draw current through fail safe coil 364 to trip interruptingdevice 315, the current is first drawn through fuse 368, which maycomprise a regular fuse, a fusible resistor or any other fusibleelement, such as a drip of solder. If interrupting device 315 fails toopen and, in particular, open in a very short amount of time, thecurrent being drawn through fuse 368 will destroy the fuse, i.e., causean open-circuit, and the current will no longer flow, leaving no furtheropportunities for the programmable device 301 to trip interruptingdevice 315.

If both methods (a) and (b) above are employed for tripping interruptingdevice 315 in the event of an EOL condition, both coils, 362, 364 ofdual coil solenoid 366 are energized. Further, if either of the twomethods, (a) and (b), successfully opens interrupting device 315, or ifinterrupting device was otherwise already open, power-on indicatorcircuit 321 will be OFF. For example, in the embodiment shown in FIG.27, power on indicator circuit includes LED 322 in series with resistor323 and diode 324. One lead of LED 322 is connected to the neutral faceterminal 344 and one lead of diode 324 is connected to phase faceterminal 342. Accordingly, when power is available at the faceterminals, current is drawn through the power on circuit on eachalternating half-cycle of AC power, thus, making LED 322 blink. If, onthe other hand, power is not available at the face terminals 342, 344,for example, because interrupting device 315 is open, or tripped, thenLED 322 will be dark, or not illuminated.

Additional embodiments and aspects thereof, related to theauto-monitoring functionality consistent with the present invention, aswell as further discussion of some of the aspects already described, areprovided below.

For example, the sinusoidal AC waveform includes two half-cycles, apositive half-cycle and a negative half-cycle. The so-called firinghalf-cycle refers to the particular half-cycle, either positive ornegative, during which a gate trigger signal to an SCR, for example SCR360 and/or SCR 320, results in the respective solenoid coil conductingcurrent and the solenoid firing, e.g., where the armature moves. Anon-firing half-cycle refers to the alternate half-cycle of the ACwaveform, i.e., either negative or positive, where current does not flowthrough an SCR or its respective solenoid coil, regardless of whether ornot the SCR gate is triggered. Whether the positive or negativehalf-cycle is the firing half-cycle is typically determined by a diodeplaced in series with the respective solenoid coil.

Under optimal conditions the auto-monitoring routine consistent withembodiments of the invention can be performed at any time within a givenAC cycle, that is, during either the positive or negative (firing ornon-firing) half-cycle. Of course, it would be ideal if theauto-monitoring routine could be completed entirely during thenon-firing half-cycle, so that any unintentional firing of the solenoid,for example, due to inadvertent SCR triggering, is avoided. Such anideal situation may not be possible, however, due to, for example,inadequate voltage sampling times by the programmable device, how thecircuit is configured, and/or how the GFCI device is powered.

One unfavorable scenario occurs when the auto-monitoring routine isperformed only during the firing half-cycle of the solenoid.Accordingly, the programmable device according to at least one exemplaryembodiment of the present invention is able to turn ON the test current,e.g., on independent, third, line 356, sample a voltage level, e.g., atthe ADC input of device 301, make a determination whether the routinehas passed, and then turn OFF the test current, all within a very smalltime period so as not to trigger the SCR during a firing half-cycle. Theauto-monitoring circuit according to this embodiment, e.g., circuit 370,operates in this condition and as such one auto-monitoring event iscompleted within 250 microseconds.

According to a further embodiment of a circuit interrupting deviceconsistent with the invention, programmable device 301 also canoptionally monitor the AC power input to the device. For example, thedevice can monitor the 60 Hz AC input that is electrically connected tothe phase and neutral line terminals 326, 328.

A full AC cycle at 60 Hz takes approximately 16.333 milliseconds tocomplete. Thus, to monitor and confirm receipt and stabilization of theAC waveform, a timer/counter within programmable device 301 isimplemented. For example, within a 100 millisecond window there shouldbe at least 6 positive transitions of a 60 Hz signal. However, becauseAC frequencies may fluctuate at 60 Hz, the qualifying event count, e.g.,to determine that AC power has been applied to the device, is set toless than 6 such transitions, for example, 3 positive transitions.Accordingly, the situation is accommodated where a circuit interruptingdevice in accordance with the invention is connected to a variable powersource, such as a portable generator, that exhibits a lower frequency atstart-up and requires a stabilization period before the optimalfrequency, e.g., 60 Hz, is achieved.

Further, to confirm that the applied AC power waveform has stabilized atthe optimal frequency, programmable device 301 counts the number ofpositive transitions repetitively occurring within a given period, forexample 6 transitions within a 100 millisecond period. If the frequencyis not stabilized at the optimal frequency, or at least not within anacceptable range, the initiation of the auto-monitoring routine isdelayed until the frequency is stabilized. If the frequency does notachieve the optimal frequency, or a frequency within an acceptablerange, within a predetermined time, a fail tally is incremented. Similarto the fail tally discussed previously with respect to theauto-monitoring routine, if the tally reaches a given threshold, theprogrammable device 301 can declare EOL.

As described above, according to at least one exemplary embodiment,programmable device 301 is implemented in a microprocessor. Because somemicroprocessors include non-volatile memory, e.g., for storing variousdata, etc., in the event of a power outage, according to a furtherembodiment all events, timers, tallies and/or states within thenon-volatile memory are cleared upon power-up of the device.Accordingly, if the fail tally or other condition resulted from improperdevice installation, inadequate or improper power, or some othernon-fatal condition with respect to the circuit interrupting deviceitself, the fail tally would be reset on power-up, when the tallyincrementing event may no longer be preset. Of course, another way ofavoiding this potential issue is to utilize a programmable device thatdoes not have non-volatile memory.

While various embodiments have been chosen to illustrate the invention,it will be understood by those skilled in the art that othermodifications may be made without departing from the scope of theinvention as defined by the appended claims. Several possiblemodifications are mentioned below by way of example only.

The reset switch may take forms other than two contact pads 144 on thecircuit board and a bridging contact 172 on the carriage. For example,the reset switch could comprise a single contact on the circuit boardclosable with a single contact on the underside of the carriage, whichcould be connected to another part of the circuit by a flexible jumperwire. Alternatively, the reset switch could be a self-containedmomentary switch mounted on or beneath the circuit board and having aprotruding stem that would be depressed by the carriage near the end ofits downward travel. Another alternative could be a proximity switchmounted on the circuit board that would close when the carriage comeswithin triggering range of the switch.

The latching mechanism could take forms other than a shouldered collar241 on the reset plunger and resilient, shouldered latch beams 192 andreset beams 206 on the carriage. For example, shouldered resilient beamsor their equivalents could be located on the reset plunger and matingfixed shoulders could be located on the carriage latching portion, withthe armature modified to retract the resilient beams as it movesdownward. Alternatively, the reset plunger could be made hollow so thatthe armature moves within it to retract plunger-mounted latchingelements, rather than vice versa. Other suitable variations will beapparent to those skilled in the art.

What is claimed is:
 1. A circuit interrupting device comprising: a pairof conductive line terminals for connecting to an AC power source; apair of line conductors, each electrically coupled to a respective oneof said conductive line terminals; a test conductor electricallyisolated from said pair of line conductors; a pair of conductive faceterminals configured to receive mating conductors of an electrical load;a fault detection circuit including at least one transformer coilthrough which each of said pair of line conductors and said testconductor traverse, said fault detection circuit being configured todetect a net current passing through the at least one transformer andgenerate a fault detection signal; an interrupting device operable toelectrically couple said pair of line conductors and said pair of faceterminals; an actuator operable to engage said interrupting device toelectrically decouple said pair of line conductors and said pair of faceterminals; and an auto-monitoring circuit electrically coupled to saidfault detection circuit and said actuator, wherein said auto-monitoringcircuit generates a test net current on said test conductor anddetermines whether said fault detection circuit successfully detects thetest net current passing through the at least one transformer coil. 2.The circuit interrupting device recited in claim 1, further comprising afirst switching device electrically coupled between said actuator andsaid fault detection circuit, and being activated when said faultdetection circuit detects a net current passing through the at least onetransformer coil; a second switching device electrically coupled betweensaid actuator and said auto-monitoring circuit, and being activated whensaid fault detection circuit fails to detect a net current passingthrough the at least one transformer coil; and a third switching deviceelectrically coupled between said test conductor and saidauto-monitoring circuit.
 3. The circuit interrupting device recited inclaim 2, further comprising a reset switch electrically coupled betweensaid fault detection circuit and said first switching device, and beingactivated when said reset switch is closed.
 4. The circuit interruptingdevice recited in claim 2, wherein said auto-monitoring circuitcontrollably closes said third switching device to generate said testnet current on said test conductor, and controllably opens said thirdswitching device to stop said test net current from being generated onsaid test conductor.
 5. The circuit interrupting device recited in claim1, wherein said fault detection circuit generates first and secondoutput signals, said first output signal being electrically coupled to afirst switch for driving said actuator when said net current passesthrough the at least one transformer and said second output signal beingelectrically coupled to said auto-monitoring circuit.
 6. The circuitinterrupting device recited in claim 5, wherein said second outputsignal is generated before said first output signal is generated, saidauto-monitoring circuit determining whether said test net current wasdetected by said fault detection circuit based on said second outputsignal.
 7. The circuit interrupting device recited in claim 6, whereinsaid auto-monitoring circuit includes a programmable device having afirst input/output (I/O) port that is controllably switched betweenbeing an input port and an output port, said second output signal ofsaid fault detection circuit being input to said first I/O port when itis controlled to be an input.
 8. The circuit interrupting device recitedin claim 1, wherein said auto-monitoring circuit includes a programmabledevice programmed to periodically run an auto-monitoring routine, saidauto-monitoring routine including generating the test net current onsaid test conductor on either a positive half-cycle of the AC power or anegative half-cycle of the AC power, and determining whether said faultdetection circuit successfully detected the test net current passingthrough the at least one transformer coil, said programmable devicefurther maintaining a failure count representing a number of times thefault detection circuit failed to detect the test net current.
 9. Thecircuit interrupting device recited in claim 8, further comprising anend-of-life indicator controlled by said auto-monitoring circuit, andbeing activated when said failure count exceeds a predeterminedthreshold.
 10. The circuit interrupting device recited in claim 3,further comprising a status determining circuit configured to determineone or more of whether power is available at the fault detectioncircuit, whether power is available at the face terminals, and whetherthe reset switch has been activated.
 11. A circuit interrupting devicecomprising: two sets of electrical contacts, each set of electricalcontacts having a fixed contact and at least one movable contact biasedaway from the fixed contact; a latch assembly including a carriageoperable to hold one of the movable contacts from each of said sets ofelectrical contacts, and first and second sets of rigid beams; a resetassembly including a user accessible reset button and a plunger having areset flange with an upper surface and a lower surface, said uppersurface engaging said first set of rigid beams when said reset button ispressed and said lower surface engaging said second set of rigid beamswhen said reset button is released; an auto-monitoring circuitelectrically coupled to said latch and reset assemblies, and configuredto automatically determine whether said circuit interrupting device isoperating properly.
 12. The circuit interrupting device recited in claim11, further comprising an actuator having a hollow central core alongits central axis and an armature movable within said central core whensaid actuator is electrically activated, wherein said armaturedisengages said lower surface of said reset flange and said first set ofrigid beams.
 13. The circuit interrupting device recited in claim 12,wherein said upper surface of said reset flange engages said second setof rigid beams when said lower surface of said reset flange isdisengaged from said first set of rigid beams.
 14. The circuitinterrupting device recited in claim 12, wherein said latch assemblyfurther includes an electrically conductive contact portion coupled to abottom surface of said carriage, and electrically completing a drivecircuit configured to activate said actuator.
 15. An auto-monitoringcircuit for automatically monitoring the performance of a ground faultcircuit interrupting (GFCI) device comprising: a microprocessorconfigured to periodically run an auto-monitoring routine based on astored program; a driver coupled to said microprocessor and beingoperable to initiate a test signal representative of a ground fault eachtime said auto-monitoring routine is run; and an end-of-life indicatorcoupled to said microprocessor and being operable to indicate that theGFCI device has failed to detect said test signal in a predeterminednumber of consecutive runs of said auto-monitoring routine, wherein saidmicroprocessor directly drives said end-of-life indicator.
 16. Theauto-monitoring circuit recited in claim 15, wherein said microprocessorincludes at least one input/output (I/O) port configurable to be eitheran input or an output port based on said auto-monitoring routine, one ofsaid configurable I/O ports being configured as an input to ananalog-to-digital converter to receive a detection signal indicatingwhether or not said test signal has been detected.
 17. A method ofoperating a circuit interrupting device comprising the steps of:periodically running an auto-monitoring routine during which a testcurrent is passed through a sense transformer; generating a secondarycurrent at said sense transformer when said test current passes throughsaid sense transformer; detecting said secondary current; generatingfirst and second detection signals when said secondary current isdetected; measuring said second detection signal; determining if saidtest current was successfully detected based on a result of saidmeasuring said second detection signal; generating a fail count based onthe result of said determining step, and representing the number oftimes the periodic test current was not detected; tripping said circuitinterrupting device if said fail count reaches a predetermined thresholdwithin a predetermined amount of time; and preventing the circuitinterrupting device from being tripped by said first detection signal ifsaid fail count reaches a predetermined threshold within a predeterminedamount of time.
 18. The method recited in claim 17, wherein saidauto-monitoring routine is run about every three seconds.
 19. The methodrecited in claim 17, further comprising the steps of: detecting adifference in current flowing in two respective line conductors;creating a first magnetic force to trip said interrupting device whensaid difference in current is detected; and creating a second magneticforce, greater than said first magnetic force, when said fail countreaches said predetermined threshold within the predetermined amount oftime.
 20. The method recited in claim 17, further comprising the step ofdirectly driving an actuator drive device to trip said circuitinterrupting device when a reset button is pressed.
 21. A circuitinterrupting device comprising: a hot conductive line terminal forconnecting to the hot conductor of an AC power source; a neutralconductive line terminal for connecting to the neutral conductor of anAC power source; line conducting means for carrying current either fromor to each of said hot conductive line terminal and said neutralconductive line terminal; detection means for detecting a net currentpassing through a transformer and generating a detection signal whensuch detection occurs; test conductor means electrically isolated fromsaid line conducting means for carrying a test net current through saidtransformer; and auto-monitoring means for generating said test netcurrent and, determining if said detection means is successfullydetecting said test net current.
 22. The circuit interrupting devicerecited in claim 21, further comprising a latch means for tripping saidcircuit interrupting device.
 23. The circuit interrupting device recitedin claim 22, wherein said latch means is driven by said detection means,or said auto-monitoring means, or both said detection means and saidauto-monitoring means.